Characterization of flip chip interconnect failure modes using high frequency acoustic micro imaging with correlative analysis

An automated ultrasonic inspection approach for flip chip solder joint assessment

“…An image is constructed based on the reflected echo, thus the intensity level of the image is proportional to the ultrasound signal reflection strength [5]. The reflected ultrasound signal contains multiple echoes representing different interface layers [10].…”

“…Also, the solder interconnections of flip chip assemblies are hidden under the silicon die and introduce complex test challenges. Several non destructive testing techniques such as X-ray inspection [4], Acoustic Micro Imaging [5] and Laser ultrasound coupled to interferometry [6] have been used to try to evaluate flip chip solder joint reliability. Nevertheless, each method only resolves certain failure types and therefore innovative advances to existing techniques are key to further understanding of failure mechanisms.…”

“…This is due to its strong penetration capabilities which enable detection of discontinuities within materials and interconnect [5,7,8]. However, the inspection process is usually performed by a human observer; where defect identification and the quality of detection are largely dependent on an operator's experience and their consistency of judgment [9].…”

Fusion of acoustic and X-ray image features for solder joint through-life monitoring during thermal cycling tests

“…An image is constructed based on the strength of the reflected echoes. The intensity level of the image is affected by the acoustic impedance mismatch and is proportional to the reflection strength of the waves [4]. Since a laminar crack on the solder joint produces an air gap that causes a larger acoustic impedance mismatch, a stronger reflection echo is received showing as a higher intensity in an image.…”

“…X-ray data can reveal certain shape and solder void alteration during thermal cycling. Alternatively, AMI is an effective approach for detecting gap-type defects such as laminar cracks due to strong reflections of ultrasound at a solid-air interface [4] [5].…”